MicroElectroMechanical Systems (MEMS) are systems that are micromachined in silicon and can be integrated with electronic microcircuits. MEMS generally fall into the two categories of microsensors and microactuators, depending on application, and in operations are based on electrostatic, electromagnetic, thermoelastic, piezoelectric, or piezoresistive effects.
MEMS often include a closed chamber, sealed membrane, or other fluid passageway and this can be found to be susceptible to differential pressure. This pressure difference can occur during various stages in a device lifetime from processing, storage, shipping to operation. The pressure difference can be caused by trapped pressure, temperature change, outgassing of materials or active operation (such as pumping or priming). The pressure difference can include bulging or collapsed membranes, trapped bubbles or fluids, or even failures such as cracking or bursting.
According to various exemplary embodiments a method of forming a MEMS is provided that forms an actuator and a first (lower) chamber to maintain the actuator. A vent is formed connecting the first chamber to the external atmosphere surrounding the system to equalize pressure within the first chamber or to allow pressure equalization to occur outside a normal operating cycle of the sealed actuator chamber. A flexible member is formed at the top of the first chamber and a second chamber is formed above the first chamber. The second chamber can be adapted to maintain a fluid, such as ink for an ink jet printing device. The flexible member separates the first chamber from the second chamber. A nozzle opening can be formed at the top of the second chamber to allow the fluid to be expelled from the nozzle when the actuator operates. Note that although a fluid ejector is described, this can be applied to any membrane system where the differential pressure needs to be managed.
According to various exemplary embodiments a MEMS has at least one vent connected to at least one sealed actuator chamber. The vent is formed to include a chamber (e.g., lollipop-shaped chamber) that has a size and shape to allow pressure equalization to occur outside a normal operating cycle of the sealed actuator chamber. A plurality of sealed actuator chambers can be connected to a single vent and, for example, the sealed actuator chambers can be positioned in one or more rows with vents positioned at ends of the rows. A vent passage connects the sealed actuator chamber to the vent. The vent can also comprise a conduit for electrical conductor lines. The vent can include a ruptured sacrificial membrane that is opened to connect the vent with the atmosphere surrounding the MEMS.
These and other features are described in, or are apparent from, the following detailed description of various exemplary embodiments of systems and methods.